How do I locate the ecm/ecu in my 2001 monte carlo ss?

I'm trying to save myself a bit of money by locating and removing the ecu (electronic control unit) from my 2001 Monte Carlo SS myself, and sending it in to be rebuilt/reprogrammed. I'll manage to save $1000 by doing this, since the dealership wants $1200, and the garage wants another $60 just to unplug it and use a screwdriver. a mechanic told me it was behind the air filter. I need to know what it looks like and if it's simple to remove/replace. Any knowledgeable folks out there who've done this and can walk me through it?|||its only a square box at the back of your air filter, it says it right on it.